• Semiar Reports

    Read More

Proton Exchange Membrane Fuel Seminar Report



Polymer electrolyte membrane fuel cells (PEMFCs) are considered a possible answer to environmental and energy problems, and are expected to soon become the most promising energy converters for automotive, stationary, and portable applications, because of their high-energy density at low operating temperatures, quick start-up and zero emissions. Consequently PEMFCs have increasingly been cited by governments as a possible pathway to the reduction of greenhouse gas emissions.At present, despite the great advances in PEMFC technology over the past two decades through intensive research and development activities, their large-scale commercialization is still hampered by their higher materials cost and lower reliability and durability. The operating principle of a PEMFC is as follows: at the anode, fuel H 2 is oxidized liberating electrons and producing protons. The electrons and protons flow via the external circuit and via proton exchange membrane inserted tightly between the anode and the cathode, respectively, to the cathode, where they combine with the dissolved oxidant O 2 to produce water and heat. Current membrane technologyrequires that the membrane be fully hydrated toensure high proton conductivity. In a PEM fuel cell, watergeneration as a product of electrochemical reaction occurs onthe cathode side. Depending upon the local thermodynamicproperties water changes its phase and the associated heatand mass transfer takes place. Excess water if not effectivelyremoved will lead to a state called flooding in which pores ofthe gas diffusion layer are blocked to species diffusion and thecatalyst active surface is covered with liquid water reducingthe total area available for reaction. Water management refersto maintaining sufficient amount of water in the cell tohydrate the membrane while removing the excess to avoidflooding.Water management is of vital importance to achieve maximum performance and durability from PEMFCs. On the one hand, to maintain good proton conductivity, the relative humidity of inlet gases is typically held at a large value to ensure that the membrane remains fully hydrated. On the other hand, the pores of the catalyst layer (CL) and the gas diffusion layer (GDL) are frequently flooded by excessive liquid water, resulting in a higher mass transport resistance. Thus a subtle equilibrium has to be maintained between membrane drying and liquid water flooding to prevent fuel cell degradation and guarantee a high performance level.

The fuel cell flooding occurs not only in the cathode and anode side, but also in the gas flow channels of the flow field as well, depending on the interplay of the properties and engineering of those components and the operating conditions. Flow channels flooding can also hinder the reactant gas ingress to the porous electrodes and impair the power output of the fuel cell. Besides, when multiple parallel channels are used flow channels flooding in one of the channels could lead to starved regions with multiple consequences. An appropriate flow channels design plays a major role in the water management problems, because the water transported from the GDL must be removed out of the cell system via these flow channels, which has been considered to be the most successful strategy for dealing with water flooding issues. The type of flow distributor used plays a major role in determining the distribution of liquid water in the cell. A PEM fuel cell with three different types of flow distributors namely parallel, serpentine and mixed flow distributors are modeled and numericallysimulated to find out the water formation and distribution characteristics.An ideal flow channel design should provide a uniform concentration of reactants and a reasonably small pressure drop between the inlet and outlet of the channel to minimize the parasitic losses and also should maintain the membrane in enough hydratedcondition over the entire cell avoiding membrane dehydration.







Download Link beloew :



Download




Similiar seminar Topics

26 page

GPRS Technology

22 page

Fuel Cell

22 page

Adaptive optics





comments powered by Disqus